It is most desirable in wound treatment to provide an adhesive dressing which will maintain the desired moist environment promoting healing while preventing scab formation; and also permitting removal of wound fluid which can build up to a pressure bubble beneath the dressing, thereby undermining the adhesive seal to the skin and thus increasing the possibility of the wound being contacted by ambient contaminants, including, of course, microorganisms which can cause infection.
Seemingly, these two objectives are often at cross-purposes so that one of the two desired objectives is accomplished to the detriment of the other.
Yet, dressings fulfilling both objectives are heretofore disclosed in the art.
By way of illustration, reference is made to U.S. Pat. No. 4,541,426 issued to Webster whose discussion of the prior art as background to the invention is additionally worth mentioning.
As stated in Col. 1 of the patent:
It has long been a recognized problem that dressings are inclined to suffer from either or both the disadvantages that they sometimes tend to float away from a wound or else they sometimes tend to adhere to the wound surface.
The first of these disadvantages generally occurs when the wound is one that produces large volumes of exudate. Generally the method of overcoming this problem is to provide the dressing with holes so that the exudate can escape and the dressing remain in contact with the wound. Certain attempts to achieve this end are disclosed in U.K. Pat. Nos. 778813, 1298011, 1408345 and U.D. Patent Application Nos. 2061732 and 2074029. One successful dressing is Melolin (Trad make. available from T. H. Smith and Nephew Ltd., Hull, U.K.) which comprises a perforated synthetic polymer film and anabsorent cellulosic pad. The perforated film is placed next to the exuding wound, the exudate passes through the perforations and is absorbed by the pad. A more recent suggestion has been to use a perforated polytetrafluoroethylene film in an effort to minimise the risk of any adherency of the dressing to the wound.
Alternatively dressings have ben suggested which comprise a thin hydrophobic film laminated to a fibrous absorbent layer. The film contains a number of apertures in the form of slits. Such dressings are described in, for example, British Pat. Nos. 815,121 and 1,163,452 and U.S. Pat. No. 3,602,220. However dressings of that type have not been found to be satisfactory because either the slits do not open or do not open wide enough to allow passage of exudate through the film to the absorbent.
The second of the aforementioned disadvantages generally occurs when the wound has dried out due to lack of production of exudate. Generally the method of overcoming this problem is to provide the dressing with a continuous layer which retards the rate of loss of water. One effective method of achieving this end is described in British Pat. No. 1280631.
However none of the known methods are free of disadvantages since what may be an excellent dressing for one kind of wound will be unsuitable for many other wounds since wounds differ greatly in their output of exudate. It has now been realised that, none only is there a need of a dressing which is suitable for use on a number of different wound types, there is also a need for a dressing which can better cope with the variation in rate of exudate production from a given wound. A dressing has now been discovered which allows passage of a greater amount of exudate from a wound which produces greater amounts of exudate and which aids in allowing the wound to remain a moist wound when it produces only smaller amounts of exudate so that it does not float away from the moist surface and has a reduced tendency to adhere to the wound. The new dressing has been found to aid in the re-epithelialisation of the wound.
Accordingly, the patented invention is said to provide a dressing comprising a conformable film with apertures therethrough characterized in that the film comprises a first layer laminated to a second layer, the first layer comprising a material which swells when in contact with water and the second layer comprising a material which when in contact with water does not swell or swells less than the first layer. According to the patentee the apertures are enlarged when in use on a wet surface and otherwise not enlarged, the enlarged openings permitting passage of water, e.g. wound exudate, the apertures when not enlarged preventing the wound from drying out; i.e. providing a moist environment.
U.S. Pat. No. 5,086,764 issued to Thomas H. Gilman Feb. 11, 1992 and assigned to The Kendall Company, assignee of the present invention describes and claims a composite dressing comprising a base sheet for placement on the skin surrounding a wound, the base sheet having an adhesive on a front surface thereof for securing the dressing to the skin, the base sheet having an opening extending therethrough for venting wound exudate, an absorbent layer separate from the base sheet and located on a back surface of the base sheet, the absorbent layer covering the opening to permit replacement of the absorbent layer without removal of the base sheet from the patient's skin, and a back sheet covering the absorbent layer, the back sheet being releasably secured to the base sheet.
Another embodiment of a composite vented dressing permitting removal of wound fluids while maintaining a moist environment is described and claimed in copending application of Thomas H. Gilman, Ser. No. 337,591 filed Apr. 13, 1989 and now U.S. Pat. No. 5,106,362, also assigned to the common assignee.
As disclosed therein, the dressing will comprise: a base sheet for contacting the skin, the base sheet having an opening for placement over a wound and adhesive means for securing the base sheet to the skin; and vent means for providing controlled leakage of fluid along a path from the wound through the opening of the base sheet, the vent means comprising cover means covering the opening, the cover means permitting passage of wound fluid therethrough while reducing evaporation through the opening and thereby helping to insure a moist environment when excess wound fluid is removed from the wound.
The dressing may have an absorbent fabric layer secured around its periphery to the back surface of the base sheet.
U.S. Pat. No. 5,056,510 of Thomas H. Gilman describes and claims a composite wound dressing comprising a base sheet having at least one opening adapted for placement over a wound, vent means for providing controlled leakage of wound fluid along a path from the wound through each of the openings of the base sheet, the vent means permitting passage of wound fluid therethrough while reducing evaporation through each opening to help insure a moist environment when excess wound fluid is removed from the wound, a cover element secured to the dressing over the base sheet and vent means, the cover element defining a chamber into which wound fluids leaking through the vent means can wick or diffuse, and a fabric reservoir for receiving and retaining wound fluids within the chamber.
Finally, a particularly efficacious composite vented dressing for removing excess wound fluids while maintaining a moist environment conducive to wound healing is disclosed in the copending application of Hamzeh Karami and Thomas H. Gilman, Ser. No. 738,983 filed Jul. 29, 1991 and also assigned to the common assignee.
As is described and claimed therein, the vented wound dressing comprises a thin conformable sheet material, at least a portion of which is adapted for placement over a wound having a pressure-sensitive adhesive layer on one surface thereof, the adhesive layer being applied to provide repeating spaced areas free of adhesive. Preferably the non-adhesive areas are arranged in a geometric pattern. In any case, while the non-adhesive areas are shown for purposes of illustration as being generally circular, the configuration is not critical and they may be of any desired shape, e.g. oval, rectangular, arcuate, etc.
At least a portion of the repeating areas of no adhesive have slits extending through the thickness thereof to permit transfer of wound fluids through the sheet material unimpeded by the presence of adhesive material which can clog the slits and thereby inhibit fluid transfer therethrough.
As is further described and claimed therein, the aforementioned vented dressing will additionally contain thereover an absorbent pad or the like providing a reservoir for receiving and retaining wound fluids diffusing through the slits in the primary dressing. Most preferably, a cover sheet providing a bacterial barrier is situated over the reservoir.
Common to all the composite dressings described above and assigned to The Kendall Company, assignee of this invention, is the concept of providing a vented dressing for placement on the skin and covering the wound, hereinafter referred to as the "primary dressing" over which is releasably secured by a pressure-sensitive adhesive what is hereinafter referred to as the "secondary dressing" and which includes a reservoir containing an absorbent fabric and which has an outer cover. As disclosed in each of these cases, the primary dressing permits diffusion of wound exudate to the overlying secondary dressing while maintaining a moist environment. Also, as disclosed in each of these cases, the secondary dressing is intended to receive and to retain wound exudate diffusing thereto through the underlying primary dressing.
In the composite primary/secondary dressings described above it is most desirable for the secondary dressing to be removable from the primary dressing in order to observe the progress in wound healing and/or to replace the secondary dressing with a fresh new one on an as needed basis when the old one becomes or is about to become saturated with wound exudate.
More particularly, it is most desirable that the secondary dressing be readily removable without pulling or tugging so as to dislodge the primary dressing or irritate the healing wound.
It has been found, however, that the adhesive bond between the two dressings for securing the secondary dressing over the primary dressing does not permit separation for removing the secondary dressing as easily as desired.